The Grim Adventures of Billy & Mandy

The series is centered around the exploits of Billy, a dimwitted and happy-go-lucky boy; Mandy, a cynical and merciless girl, and Grim, the Grim Reaper who is often tormented by the duo. After cheating at a limbo match against Grim (in retaliation for putting the limbo rod too low for them to go under), he is enslaved in a permanently unwanted friendship with the children.